The human skin is populated by a large variety of microorganisms that mainly live as commensals in a relatively stable composition on the surface of the skin. This normal skin flora is termed “resident skin flora” and supports the healthy appearance of the skin, which is shiny and sufficiently moist. In addition to creating a natural barrier for retaining moisture within the epidermis, the normal skin flora protects the skin against the intrusion of potentially pathogenic microorganisms.
Among the microorganisms constituting the resident microbial flora of healthy skin, often more than ninety percent thereof are Staphylococcus epidermidis (coagulase negative), Micrococcus spec., Diphteroids and propionibacteria. A typical imbalance of the skin microflora is for example observed when Staphylococcus aureus populates the skin microflora to an increasing extent, as a result of which the skin is increasingly prone to dryness. In this condition, the epidermis displays cracks and tends to show red areas as a result of inflammation. The danger of colonization by pathogenic microorganisms increases drastically in the case of small lesions or other damages on the surface of the skin, especially when the normal skin flora is diminished as a result of frequent washing, make-up, UV-light, or by antibiotics.
Thus, the microbial skin flora affects several factors of the skin that are of cosmetic relevance, namely the pH value of the skin, the barrier function and the skin's lipid content. In this respect, S. epidermidis assists the skin in fighting against pathogenic microorganisms by lowering the pH to values at which pathogens are not able to effectively grow. The water barrier function and the lipid content of the skin, on the other hand, depend on the ceramide content of the horny layers. Lowering of the ceramide content leads to a dried out and cracked skin condition. In this respect, a study conducted on atopical dermatitis patients having such a skin condition revealed that Staphylococcus aureus may dominate the microbial skin flora under these circumstances. In particular, it was found that as opposed to normal commensals of the skin, this pathogen displays a very high ceramidase activity. Under these conditions, the loss of humidity and lipids leads to the generation of inflammation of the epidermis.
WO 2006/136420 A2 relates to microorganisms, and in particular to microorganisms belonging to the genus Lactobacillus, which are able to stimulate the growth of one or more microorganisms of the resident skin microbial flora and which does not stimulate the growth of microorganisms of the transient pathogenic micro flora, as well as to the use of such microorganisms in cosmetic and pharmaceutical compositions, in particular for the treatment of dermatitis.
There however remains the need for a compound or composition which does not depend on cell cultures requiring special care and handling, and which are thus limited with respect to their application. In particular, the need exists for a compound or composition which may be easily produced in a cost-effective manner. Furthermore there is a need for a compound or composition which displays a low effective dose with respect to its beneficial effects, not only in view of providing more cost-effective cosmetic formulation, but also for opening new perspectives with respect to new applications in the field of both cosmetics and pharmaceuticals.